Free piston paraffin scraper



INVENTOR ATTORNEY July 22, 1969 H. D. NETTLr-:s

FREE PISTON PARAFFIN SCRAPER Filed oct. 5, 1967 FIG. 2

HENRY D. NETTLES IUnited States Patent O 3,456,727 FREE PISTON PARAFFIN SCRAPER Henry D. Nettles, 1806 Swan St., Longview, Tex. 75601 Filed Oct. 3, 1967, Ser. No. 672,584 Int. Cl. E21b 37/02 U.S. Cl. 166-170 3 Claims ABSTRACT OF THE DISCLOSURE A tubing parain scraper having a mandrel with a central bore communicating with an open chamber dened in the bottom of the mandrel of a diameter greater than the bore. A free ball is contained in the chamber and is movable between two positions to act as a valve. A pair of parallel bars are disposed across the bottom of the chamber in order to retain the ball therein, and yet allow ow of fluid through the chamber. External rings are mounted about the mandrel and have a diameter sufcient to clear the interior walls of the tubing of parain.

During the free ascent of the scraper up the tubing, parafn is scraped from the tubing and accumulated within the central bore of the mandrel. At the top of the tubing the accumulated parain is exhausted through the end of the open chamber.

Field of the invention This invention relates to paraflin scrapers, and more particularly to free piston type paraffin Scrapers whlch freely ascend and descend within the Well tubing.

The prior art The deposit of parain upon the interior walls of oil well tubing during the owing of oil is a serious problem. Many different types of parain Scrapers have thus been heretofore devised which scrape accumulated parain from oil well tubing walls. The free piston, or rabbit, type of paraffin scraper has been found to be particularly useful to clean off the Walls of well tubings, as these Scrapers automatically ascend and descend in the-tubing with the pumping of each head of well uid to remove accumulated parain. The free piston Scrapers have also heretofore been found useful in sealing with the walls of the tubing to assist in the production of well fluids by t for blocking interior scraper passages so that the scrapers are forced upwardly when oil is owing from the well. `Parafln is removed-from the tubing walls and forced out of the pipeline outlet by ascent of the scraper. The Valves are then opened after the scraper reaches the top of .the wall to let the scraper slowly descend under its own weight. Examples of such paraffin scrapers are disclosed and described in U.S. Patent No. 2,058,825, U.S. Patent No. 2,893,493, and U.S. Patent No. 3,058,525.

The performance of piston parain Scrapers heretofore developed has not been completely satisfactory due to the fact that the Scrapers merely tend to move the parain scraped from the tubing walls upwardly and outwardly through the top of the tubing. Such large amounts of parain are sometimes removed by these Scrapers that the performance .of the scraping action is sometimes impeded, and portions of the removed paraffin sometimes tend to leak downwardly past the ascending scraper. Further, the valves utilized by parain Scrapers heretofore developed have not always been satisfactory with respect to long periods of operation, as the valves are complex in con- 3,456,727 Patented July 22, 1969 "ice In accordance -with the present invention, a free piston paraffin scraper includes a mandrel having a bore through the length thereof which communicates at a transition portion with an open bottom chamber having dimensions greater than the bore. A ball is disposed in the chamber movable between two positions and sized to seat on the transition portion in one position. A stop device is mounted in the bottom -of the chamber to retain the ball within the chamber when the ball is in a second position. An external ring is connected about the mandrel and has a diameter suliicient to clear the interior walls of a well pipe of accumulated paran.

The drawings For a more complete understanding of the present invention and for further objects and advantages thereof, reference may now be had to the following description taken in conjunction with the accompanying drawings in Referring to FIGURE 1, a conventional oil well tubing 10 extends for a distance above the surface of the ground and includes a rubber-filled bull plug 12 at the upper end thereof. An outlet pipe 14 allows the ow of oil from the tubing 10 to suitable processing and storage stations. A valve 16 in the outlet pipe 14 is controlled by a motor valve 18 in order to selectively initiate or stop the ow of oil from the tubing. A manual valve 20` is also provided in order to allow manual regulation of the flow of oil.

A parain scraper designated generally by the numeral 22 is illustrated in the bottom regions of the tubing 10 resting upon a collar stop 24. A pair of scraping rings 26 and 28 are connected about the parafn scraper 22 and are of diameters so as to iit closely within the tubing 10 without impeding movement of the scraper.

FIGURE 2 illustrates a detailed sectional view of the paraffin scraper 22. The scraper 22 comprises an elongated metal mandrel 30 having a central bore 32 along the length thereof. The central bore 32 communicates at an annular transition portion 34 with an enlarged diameter open end chamber 36. Chamber 36 encloses a free ball 38 which is adapted to act as a valve by sealingly seating against the transition portion 34. The ball 38 is heavier than a like volume of borehole fluid and is preferably constructed from material such as oil resistant rubber or plastic in order to resist the high temperatures and well bore fluids of the well.

As may be most clearly seen in FIGURE 3, a pair of parallel pins 40 and 42 are connected across the lower part of chamber 36 to retain ball 38 within the chamber. Of course, it will be apparent that a number of different retaining devices could be utilized to retain the ball within the chamber in place of the pins 40 and 42, as for instance a large mesh wire screen or the like.

` The mandrel 30 also includes in its lower end a nose t ysection 44 which is tapered to facilitate the passage of rest against the collar stop 24. The nose section 44 also includes a central bore 46 which communicates at one end with the chamber 36. Suitable fastening pins 48 attach the nose section 44 to the lower end of the mandrel 30. If desired, the nose section 44 may be replaced by tapering the lower end of the mandrel 30.

The upperV end of the mandrel 30 is annularly relieved to define a fishing neck S which allows the scraper to be retrieved from a well tubing by suitable fishing devices. The outside diameter of the iishing neck is slightly less than the overall diameter of the mandrel 30 to facilitate the passage of paraffin removed by the ring 28 into the bore 32. Anpupper portion 52 of the bore 32 is conically shaped in order to facilitate the entry of the paraiiin into the bore 32.

In operation of the paraffin scraper, the valves 16 and 20 are closed, the upper portion of the tubing 10 is removed, and the paraffin scraper 22 is dropped into the tubing. The valve 20 is then opened to allow the paratlin scraper 22 to slowly sink toward the bottom of the tubing 10 under its own weight.

The descent of the scraper will be relatively slow, due to intermittent valving action of the ball 38 within the chamber 36. When the downward speed of the paraffin scraper becomes excessively rapid, the ball 38 will be seated against the transition portion 34 by the force of the fluid passing through the bore 46, the chamber 36 and the bore 32, thereby temporarily arresting the downward movement of the paraffin scraper 22. After the motion of the paratiin scraper 22 has been substantially reduced, the ball 38 will fall under its own weight to the position illustrated in FIGURE 2, thereby again allowing passage of the borehole fluids through the interior of the paratiin scraper 22 and allowing the paraffin scraper 22 to further descend within the tubing 10. The paraflin scraper 22 will thus slowly descend downwardly in the tubing 10 until it comes in contact with the collar stop 24. At such depths, the pressure and heat upon the parain scraper 22 will melt off any parain which has accumulated upon the tool during its descent.

When it is desired to flow oil from the tubing, the valve 16 is opened to allow ow of oil through the outlet pipe 14. The force of the fluid flow will force the ball 38 upwardly to seat against the transition portion 34. The force of the liuid flow will thus push the parain scraper 22 upwardly along the tubing 10. Due to the close tit of the rings 26 and 28, the parafiin which has accumulated upon the interior walls of the tubing 10 will be removed.

Some of the para'lin removed by the rings 26 and 28 will be forced ahead of the upwardly moving paratiin scraper 22, while a portion of the removed paratiin will enter the bore 32 through the conical entrance 52 of the mandrel 30. A quantity of paraflin will thus be accumulated Within the bore 32 during the ascent of the parain scraper 22, thereby preventing amounts of the parain scraped from the walls from passing between the rings 26 and 28 and the interior Walls of the tubing 10 and escaping below the ascending paraiiin scraper 22. For some applications, it may be desirable to combine rings 26 and 28 into an elongated single ring about mandrel 30.

The paraiiin scraper 22 will continue to ascend as long as the Valve 16 is open until the top of the paraffin scraper 22 cornes in contact with the resilient bull plug 12. The bull plug is rubber-filled in order to cushion the impact of the paraffin scraper 22. After the scraper 22 comes to rest against'bull plug 12, the ball 38 will fall downwardly against pins 40 and 42, thereby opening the lower end of bore 32. Pins 40 and 42 are spaced above the opening to bore 46 so that ball 38 cannot block 46 when in its downward position.

vThe length of the parain scraper 22 is such that the nose section 44 will be disposed in the region of the opening to thevoutlet pipe'14.' The passage of the borehole iluid past the end of the nose section 44 and throughthe outlet pipe 14 creates a'suction in the bore 46, thereby tending to exhaust the accumulated parainwithin the bore 32 from the paratiin scraper. The accumulated parain within the bore 32 is then -swept outwardly through the outlet pipe 14 by theow of fluid.

After the accumulated parafn within thebore 32 has been exhausted and the desired amount of borehole fluid has been flowed out of the tubing 1 0, the valve 16 will be shut and theparaiiin scraper 22'will again begin its free descent downwardly to the lower regionsvof the tubing 10.

Whereas the present specification has beenV described in detail with respect to a certain embodiment, it will'b'e understood that variations and modifications may besuggested to personsskilled in the art which will not depart from the scope of the invention as deiined inthe appended v claims.

What is claimed is: v t 1. A free piston'p'arain scraper for well tubing orn arising: j

(a.) a mandrel having a bore through the length thereof communicating at the lowerfendthereof ata trnsition portion with an open bottom chamber which has a diameter larger than said 'b ore, said' bore "having an open upper end shaped to receive paratiinfscraped from the walls of the well tubing when said mandrel moves upwardlyin the well tubing, Y (b) a ball having a weightheavier than a like volume of borehole tluid disposed withinsaid chamber for free unimpeded movement within' the said chamber between upper and lower positions, said ball adapted to seat on said transition portion in theupper position to cause upward movement of said mandrel in the well tubing, (c) at least one bar extending across a lower part of said chamber for maintaining space between said ball and said open bottom to allow uid iiow through said bore when the ball is in the lower position, (d) a generally resilient nose cone portion on the lower end of said mandrel with a bore therethrough, and (e) external ring means connected about said mandrel and having a diameter to clear the interior walls of the well tubing of parain when said mandrel moves upwardly in the well tubing, whereby parain is collected by the open upper end of said mandrel and maintained within said bore during the upward ascent of said mandrel and wherein the Aparaffin is exhausted from the lower end of said mandrel when said'man` drel reaches the top of said welltubingand said ball is in the lower position. 2. The paral'lin scraper of clairnl` wherein the open upper end of said bore has a conical shape with the major opening upward in order to receive paratiiricollected4 by said scraper. '4 f` l v v3. The paraffin scraper offclaim land furtheri'comprising: 'y

a pair of parallelbars in said chamber spaced apart for a distance less than the diameter of said ball.

References Cited UNITED STATES PATENTS 2,249,990 v 7 /1941 Tinsley c r 166-177 X 2,728,398 12/1955 Taylor-a -c c 1-166;170 2,785,757 3/.1957 .Middleton 166-170 2,838,120 6/.1958 Allmendinger et al. 1'75-'-211X 2,893,493 7/1959 Copas 166-170 2,962,978 12/1960 Reeves t 10S-"52 X DAVID BROWN, Primary Examiner 

